Bollettino valanghe

Mt Hood

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Forecast updated at 7:40 AM to reflect dangerous avalanche conditions developing with rising snow levels below treeline and more widespread wind slab activity near and particularly above treeline.

You can easily trigger a wind slab in wind-exposed terrain and it may be large by the afternoon. Expect larger avalanches where the new snow redistributes cold snow existing prior to the storm. At lower elevations, rain on snow will destabilize any dry snow above a crust, with the potential for isolated large natural avalanches on slopes steeper than 35 degrees.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Wind slabs may be more dangerous than originally forecast at upper elevations as the forecast snowfall amounts have increased into the 4-10" range for Wednesday night through Thursday.  This snow overlies a melt-freeze crust in most terrain up to 7000 ft, enabling yoou to track the slab depth above the crust using a pole or probe. Where these slabs form 6" or deeper, you can trigger an avalanche on a steep slope that you should steer around. N aspects and upper elevations have a heavily wind-affected snow surface in most locations, but fresh slabs could be touchy where they overly any less wind-affected snow. These aspects could build an isolated large slab by the afternoon. Wind patterns will be different with this storm as southerly flow focuses slabs on these same aspects on the northern half of the compass. Dial back your terrain selection as the day progresses or if you see evidence of fresh wind slabs avalanches, blowing snow, or shooting cracks. Avoid all wind-loaded slopes 35 degrees and steeper.

    (4/5/2023) Small explosive-triggered soft slabs in wind drifted snow.

    Photo: Joe Dellaporta

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    We're expecting moderate rain to fall on the snowpack up to 6000 ft. In most cases, this rain will fall on crusts and the surface snow will become wet and gloppy once the crusts break down. However, where dry snow remains below thin crusts on lower-elevation N-facing aspects, expect the possibility for a round of natural avalanches running down to the 3/31 crust. These avalanches could be large.  Avoid exposure to all slopes steeper than 35 degrees that receive rain on dry snow.

    (1/14/2023)

    A D2 (large) wet snow avalanche.

    Photo: Irene Henninger

Avalanche Discussion

We're heading into an active storm cycle with warming temperatures, denser snow, and rain on snow (at lower elevations) adding some uncertainty to the forecast. How quickly the snow levels rise and precipitation increases in intensity will influence how rapidly slabs form. With the added uncertainty, plan to dial back your terrain selection if you see anything that isn't in line with this forecast.

Another massive late-season storm brought 50-60" of snow to Mt Hood along with strong W and WNW winds (particularly on the E side of the Mountains). Intense winds and periods of heavy snowfall finally ramped down rapidly early Tuesday, but Mt Hood Meadows got impressive control results that morning.  The Accordian Avalanche released in near treeline terrain on an ESE aspect and was historically impressive, particularly for the elevation of the start zone. You can read more about it here. Avalanches such as this one are believed to be unreactive to human trigger moving forward. The slab failed on a softer layer just beneath the firm and very heavy slab with the weaker layer strengthening rapidly in the last 24 hours. Smaller soft slab pockets remained reactive to explosive triggers in control results on Wednesday. The sun came out to trigger some rollerballs on Wednesday and extended the elevation of the melt-freeze crust up to around 7000 ft on most aspects besides true north.

Last week observers reported weak snow associated with a crust that sits several feet below the snow surface. This layer was likely responsible for the isolated whumphs in the Gunsight Ridge area and propagating results( observation) near Vista Ridge. While isolated and unlikely, keep this information in mind especially if you find yourself traveling on higher elevation, northerly aspects.

Regioni coperte